Anisotropic flow coefficients and their fluctuations are investigated for Au + Au collisions at center-of-mass energy $\sqrt{s_{NN}}$ = 200 GeV by using a multiphase transport model with string melting scenario. Experimental results of azimuthal anisotropies by means of the two- and four-particle cumulants are generally well reproduced by the model including both parton cascade and hadronic rescatterings. Event-by-event treatments of the harmonic flow coefficients $v_n$ (for $n=2$, 3, and 4) are performed, in which event distributions of $v_n$ for different orders are consistent with Gaussian shapes over all centrality bins. Systematic studies on centrality, transverse momentum ($p_T$), and pseudorapidity ($\eta$) dependencies of anisotropic flows and quantitative estimations of the flow fluctuations are presented. The $p_T$ and $\eta$ dependencies of absolute fluctuations for both $v_2$ and $v_3$ follow trends similar to their flow coefficients. Relative fluctuation of triangular flow $v_3$ is slightly centrality dependent, which is quite different from that of elliptic flow $v_2$. It is observed that parton cascade has a large effect on the flow fluctuations, but hadronic scatterings make little contribution to the flow fluctuations, which indicates flow fluctuations are mainly modified during partonic evolution stage.

STAR measurements of dihadron azimuthal correlations ($\Delta \varphi$) are reported in midcentral (20–60%) Au + Au collisions at $\sqrt{s_{{}_{\mathit{NN}}}}=200$ GeV as a function of the trigger particle's azimuthal angle relative to the event plane, ${\varphi }_s=|{\varphi }_t-{\psi }_{\mathrm{EP}}|$. The elliptic ($v_2$), triangular ($v_3$), and quadratic ($v_4$) flow harmonic backgrounds are subtracted using the zero yield at minimum (ZYAM) method. The results are compared to minimum-bias d + Au collisions. It is found that a finite near-side ($\left|\Delta \varphi \right|<\pi /2$) long-range pseudorapidity correlation (ridge) is present in the in-plane direction (${\varphi }_s\sim 0$). The away-side ($\left|\Delta \varphi \right|>\pi /2$) correlation shows a modification from d + Au data, varying with ${\varphi }_s$. The modification may be a consequence of path-length-dependent jet quenching and may lead to a better understanding of high-density QCD.

We perform a detailed comparison of results of the Gamow shell model and the Gaussian expansion method supplemented by the complex scaling method for the same translationally invariant cluster-orbital shell model Hamiltonian. As a benchmark test, we calculate the ground state $0^{+}$ and the first excited state $2^{+}$ of mirror nuclei ${}^6$He and ${}^6$Be in the model space consisting of two valence nucleons in a $p$ shell outside of a ${}^4$He core. We find a good overall agreement of results obtained in these two different approaches, also for many-body resonances.

A direct $Q$-value measurement has been made at TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) for the ${}^{51}\mathrm{Cr}$($e^{-}$,${\nu }_e$)${}^{51}\mathrm{V}$ reaction. This electron capture (EC) reaction was used in calibration measurements at the solar neutrino experiments SAGE and GALLEX, and the observed event rate differed from predictions creating the so-called gallium anomaly. Using isotopes delivered by the Isotope Separator and Accelerator (ISAC) facility at TRIUMF and charge breeding them to charge states 5+ and 6+, a $Q$ value of 751.86(55) keV was determined. This represents a 1.3$\sigma$ deviation from the result in the Atomic Mass Evaluation 2012 (AME12) and the value used in the calculated event rate. This deviation is found to be insignificant in context of the gallium anomaly, thus confirming that the predicted event rate has not been overestimated as the result of an erroneous ${}^{51}\mathrm{Cr}$ EC $Q$ value. Additionally, the absolute masses of each ${}^{51}\mathrm{Cr}$ and ${}^{51}\mathrm{V}$ have been independently determined and are in agreement with the AME12 values.

In this work we study systematically the energetics and intensity distributions of Gamow-Teller (GT${}^{\pm }$) and isovector spin monopole (IVSM${}^{\pm }$) transitions from the ground states of the pairs (${}^{76}\mathrm{Ge}$,${}^{76}\mathrm{Se}$), (${}^{82}\mathrm{Se}$,${}^{82}\mathrm{Kr}$), (${}^{100}\mathrm{Mo}$,${}^{100}\mathrm{Ru}$), (${}^{116}\mathrm{Cd}$,${}^{116}\mathrm{Sn}$), (${}^{128}\mathrm{Te}$,${}^{128}\mathrm{Xe}$), (${}^{130}\mathrm{Te}$,${}^{130}\mathrm{Xe}$), and (${}^{136}\mathrm{Xe}$,${}^{136}\mathrm{Ba}$), of double-beta-decay initial and final nuclei, to the $J^{\pi }=1^{+}$ excited states of the intermediate odd-odd nuclei ${}^{76}\mathrm{As}$, ${}^{82}\mathrm{Br}$, ${}^{100}\mathrm{Tc}$, ${}^{116}\mathrm{In}$, ${}^{128,130}\mathrm{I}$, and ${}^{136}\mathrm{Cs}$. We use a proton-neutron quasiparticle random-phase approximation (QRPA) theory framework with the Bonn-A two-body interaction in large no-core single-particle valence bases. Our studies indicate that the GT${}^{-}$ strength at the giant resonance (GTGR) region and the low-energy part of the IVSM${}^{-}$ strength overlap, which could be of significance for the analyses of the ($p,n$) type of reaction experiments at and around the GTGR.

I calculate the parity violating asymmetry $A_{pv}$ for elastic electron scattering from ${}^{27}\mathrm{Al}$ in order to compare with the Qweak experiment “background” ${}^{27}\mathrm{Al}$ measurement. I find that Coulomb distortions, and the quadrupole form factor, reduce $A_{pv}$ near the diffraction minimum. The Qweak data can be used to confirm the neutron radius of ${}^{27}\mathrm{Al}$, if nuclear structure uncertainties are indeed small, as I suggest, and one can estimate inelastic and impurity contributions. This could provide an important check of the measurement, analysis, and theory.

The strength of the $E_{\mathrm{p}}=1.842$ MeV resonance in the ${}^{40}$Ca(p,$\gamma$)${}^{41}$Sc reaction is determined with two different methods: First, by an absolute strength measurement using calcium hydroxide targets, and second, relative to the well-determined strength of the resonance triplet at $E_{\alpha }$ = 4.5 MeV in the ${}^{40}$Ca($\alpha$,$\gamma$)${}^{44}$Ti reaction. The present new value of $\omega \gamma =(0.192\pm 0.017)$ eV is 37% (equivalent to $3.5\sigma$) higher than the evaluated literature value. In addition, the ratio of the strengths of the 1.842 MeV ${}^{40}$Ca(p,$\gamma$)${}^{41}$Sc and 4.5 MeV ${}^{40}$Ca($\alpha$,$\gamma$)${}^{44}$Ti resonances has been determined to be $0.0229\pm 0.0018$. The newly corrected strength of the 1.842-MeV resonance can be used in the future as a normalization point for experiments with calcium targets.

The incompressibility (compression modulus) $K_0$ of infinite symmetric nuclear matter at saturation density has become one of the major constraints on mean-field models of nuclear many-body systems as well as of models of high density matter in astrophysical objects and heavy-ion collisions. It is usually extracted from data on the giant monopole resonance (GMR) or calculated using theoretical models. We present a comprehensive reanalysis of recent data on GMR energies in even-even ${}^{112–124}$Sn and ${}^{106,100–116}$Cd and earlier data on $58\le A\le 208$ nuclei. The incompressibility of finite nuclei $K_A$ is calculated from experimental GMR energies and expressed in terms of $A^{-1/3}$ and the asymmetry parameter $\beta =(N-Z)/A$ as a leptodermous expansion with volume, surface, isospin, and Coulomb coefficients $K_{\mathrm{vol}}$, $K_{\mathrm{surf}}$, $K_{\tau }$, and $K_{\mathrm{Coul}}$. Only data consistent with the scaling approximation, leading to a fast converging leptodermous expansion, with negligible higher-order-term contributions to $K_A$, were used in the present analysis. Assuming that the volume coefficient $K_{\mathrm{vol}}$ is identified with $K_0$, the $K_{\mathrm{Coul}}=-(5.2\pm 0.7)$ MeV and the contribution from the curvature term $K_{\mathrm{curv}}{A}^{-2/3}$ in the expansion is neglected, compelling evidence is found for $K_0$ to be in the range 250 $<K_0<$ 315 MeV, the ratio of the surface and volume coefficients $c=K_{\mathrm{surf}}/K_{\mathrm{vol}}$ to be between $-2.4$ and $-1.6$ and $K_{\tau }$ between $-840$ and $-350$ MeV. In addition, estimation of the volume and surface parts of the isospin coefficient $K_{\tau }$, $K_{\tau ,v}$, and $K_{\tau ,s}$, is presented. We show that the generally accepted value of $K_0$ = (240 $\pm$ 20) MeV can be obtained from the fits provided $c\sim -1$, as predicted by the majority of mean-field models. However, the fits are significantly improved if $c$ is allowed to vary, leading to a range of $K_0$, extended to higher values. The results demonstrate the importance of nuclear surface properties in determination of $K_0$ from fits to the leptodermous expansion of $K_A$. A self-consistent simple (toy) model has been developed, which shows that the density dependence of the surface diffuseness of a vibrating nucleus plays a major role in determination of the ratio $K_{\mathrm{surf}}/K_{\mathrm{vol}}$ and yields predictions consistent with our findings.

The Dalitz decay $\eta \to e^{+}{e}^{-}\gamma$ has been measured in the $\gamma p\to \eta p$ reaction with the Crystal Ball and TAPS multiphoton spectrometers, together with the photon-tagging facility at the Mainz Microtron MAMI. The experimental statistic used in this work is one order of magnitude greater than in any previous measurement of $\eta \to e^{+}{e}^{-}\gamma$. The value obtained for the slope parameter ${\Lambda }^{-2}$ of the $\eta$ transition form factor, ${\Lambda }^{-2}=(1.95\pm 0.{15}_{\mathrm{stat}}\pm 0.{10}_{\mathrm{syst}})$ GeV${}^{-2}$, is in good agreement with recent measurements conducted in $\eta \to e^{+}{e}^{-}\gamma$ and $\eta \to {\mu }^{+}{\mu }^{-}\gamma$ decays, as well as with recent form-factor calculations. The uncertainty obtained in the value of ${\Lambda }^{-2}$ is lower compared to results from previous measurements of the $\eta \to e^{+}{e}^{-}\gamma$ decay.

High spin states of ${}^{88}\mathrm{Zr}$ were populated with ${}^{80}\mathrm{Se}$(${}^{13}\mathrm{C}$, $5n$) fusion evaporation reaction. A thin target as well as Au backed target were used in two different experiments for the present study. Excited levels of ${}^{88}\mathrm{Zr}$ have been observed up to spin $\sim 20\hslash$ and an excitation energy of $\sim 10$ MeV. Spin and parity of most of the states have been determined from directional correlation and polarization measurements. The level scheme was substantially extended with the addition of a number of high spin states and transitions. The comparison of the measured levels of ${}^{88}\mathrm{Zr}$ with large shell model calculations based on the full unrestricted $f_{5/2}p{g}_{9/2}$ model space established the dominance of shell-model excitation up to the highest observed spin.

The effective-interaction theory has been one of the useful and practical methods for solving nuclear many-body problems based on the shell model. Various approaches have been proposed which are constructed in terms of the so-called $\widehat{Q}$ box and its energy derivatives introduced by Kuo et al. In order to find out a method of calculating them we make a decomposition of a full Hilbert space into subspaces (the Krylov subspaces) and transform a Hamiltonian to a block-tridiagonal form. This transformation brings about much simplification of the calculation of the $\widehat{Q}$ box. In the previous work a recursion method was derived for calculating the $\widehat{Q}$ box analytically on the basis of such transformation of the Hamiltonian. In the present study, by extending the recursion method for the $\widehat{Q}$ box, we derive another recursion relation to calculate the derivatives of the $\widehat{Q}$ box of arbitrary order. With the $\widehat{Q}$ box and its derivatives thus determined we apply them to the calculation of the $E$-independent effective interaction given in the so-called Lee-Suzuki (LS) method for a system with a degenerate unperturbed energy. We show that the recursion method can also be applied to the generalized LS scheme for a system with nondegenerate unperturbed energies. If the Hilbert space is taken to be sufficiently large, the theory provides an exact way of calculating the $\widehat{Q}$ box and its derivatives. This approach enables us to perform recursive calculations for the effective interaction to arbitrary order for both systems with degenerate and nondegenerate unperturbed energies.

The neutron-induced fission cross section of ${}^{234}\mathrm{U}$ has been measured at the CERN n_TOF facility relative to the standard fission cross section of ${}^{235}\mathrm{U}$ from 20 keV to 1.4 MeV and of ${}^{238}\mathrm{U}$ from 1.4 to 200 MeV. A fast ionization chamber (FIC) was used as a fission fragment detector with a detection efficiency of no less than 97%. The high instantaneous flux and the low background characterizing the n_TOF facility resulted in wide-energy-range data (0.02 to 200 MeV), with high energy resolution, high statistics, and systematic uncertainties bellow 3%. Previous investigations around the energy of the fission threshold revealed structures attributed to $\beta$-vibrational levels, which have been confirmed by the present measurements. Theoretical calculations have been performed, employing the talys code with model parameters tuned to fairly reproduce the experimental data.

The fusion barrier distributions for ${}^{28,30}\mathrm{Si}$ + ${}^{124}\mathrm{Sn}$ systems were extracted from quasielastic excitation function measurements at backward angles. The experimental barrier distributions were then compared with coupled-channel (CC) calculations. The fusion barrier distribution for the ${}^{30}\mathrm{Si}$ + ${}^{124}\mathrm{Sn}$ reaction was well reproduced by the CC calculations with the inclusion of projectile and target inelastic couplings and only one possible positive $Q$-value 2$n$-transfer channel coupling using the ccfull code. However, CC calculations with similar coupling schemes for inelastic excitation of target and projectile with the 4$n$-transfer channel corresponding to the highest positive $Q$ value failed to reproduce the barrier distribution for the ${}^{28}\mathrm{Si}$ + ${}^{124}\mathrm{Sn}$ reaction, because it has many positive $Q$-value multi-neutron transfer channels. A better agreement between the experimental fusion barrier distribution for the ${}^{28}\mathrm{Si}$ + ${}^{124}\mathrm{Sn}$ system and the prediction of semiempirical CC calculations based on the Zagrebaev framework [V. I. Zagrebaev, Phys. Rev. C 67, 061601(R) (2003)] was obtained only after considering positive $Q$-value multi-neutron transfer couplings. The sensitivity of the fusion barrier distribution to the hexadecapole deformation parameter ${\beta }_4$ of the projectile was also discussed.

When muons travel through matter, their energy losses lead to nuclear breakup (“spallation”) processes. The delayed decays of unstable daughter nuclei produced by cosmic-ray muons are important backgrounds for low-energy astrophysical neutrino experiments, e.g., those seeking to detect solar neutrino or diffuse supernova neutrino background (DSNB) signals. Even though Super-Kamiokande has strong general cuts to reduce these spallation-induced backgrounds, the remaining rate before additional cuts for specific signals is much larger than the signal rates for kinetic energies of about 6–18 MeV. Surprisingly, there is no published calculation of the production and properties of these backgrounds in water, though there are such studies for scintillator. Using the simulation code fluka and theoretical insights, we detail how muons lose energy in water, produce secondary particles, how and where these secondaries produce isotopes, and the properties of the backgrounds from their decays. We reproduce Super-Kamiokande measurements of the total background to within a factor of 2, which is good given that the isotope yields vary by orders of magnitude and that some details of the experiment are unknown to us at this level. Our results break aggregate data into component isotopes, reveal their separate production mechanisms, and preserve correlations between them. We outline how to implement more effective background rejection techniques using this information. Reducing backgrounds in solar and DSNB studies by even a factor of a few could help lead to important new discoveries.

The properties of single-particle states in the magic nuclei ${}^{40}\mathrm{Ca}$ and ${}^{208}\mathrm{Pb}$, in particular the energies, spectroscopic factors, and the effective mass, have been studied in a fully self-consistent particle-vibration coupling (PVC) approach within the framework of Skyrme energy density functional theory. All selected phonons are obtained by the random phase approximation, and the same Skyrme interaction is also used in the PVC vertex. We focus on the effect of the noncentral two-body spin-orbit and tensor interactions on the single-particle properties. It has been found that the contributions of those terms are important to improve the results for ${}^{208}\mathrm{Pb}$. The calculated single-particle energies and spectroscopic factors are compared to available experimental data. The single-particle level density around the Fermi surface is significantly increased due to the effect of PVC.

The ${}^{14}\mathrm{C}$ + $n\leftrightarrow {}^{15}\mathrm{C}$ system has been used as a test case in the evaluation of a new method to determine spectroscopic factors that uses the asymptotic normalization coefficient (ANC). The method proved to be unsuccessful for this case. As part of this experimental program, the ANCs for the ${}^{15}$C ground state and first excited state were determined using a heavy-ion neutron transfer reaction as well as the inverse kinematics ($d$,$p$) reaction, measured at the Texas A&M Cyclotron Institute. The values $C_{2s1/2}^2=1.88\pm 0.18$ fm${}^{-1}$ for the ground state and $C_{1d5/2}^2=4.25\pm 0.38\times {10}^{-3}$ fm${}^{-1}$ for the first excited state ($E_{\text{exc}}=740$ keV) were obtained. The ANCs were used to evaluate the astrophysical direct neutron capture rate on ${}^{14}\mathrm{C}$, which was then compared with the most recent direct measurement and found to be in good agreement. A study of the ${}^{15}\mathrm{C}$ SF via its mirror nucleus ${}^{15}\mathrm{F}$ and a new insight into deuteron stripping theory are also presented.

The $b_1$ structure function is an observable feature of a spin-1 system sensitive to non-nucleonic components of the target nuclear wave function. The contributions of exchanged pions in the deuteron are estimated and found to be of measurable size for values of $x$ of about 0.1. A simple model for a hidden-color, six-quark configuration (with $\sim 0.15\%$ probability to exist in the deuteron) is proposed and found to give substantial contributions for values of $x>0.2$. Good agreement with Hermes data is obtained. Predictions are made for an upcoming JLab experiment. The Close and Kumano sum rule is investigated and found to be a useful guide to understanding various possible effects that may contribute.

The charge-exchange reaction $K^{+}\mathrm{Xe}\to K^{0}p{\mathrm{Xe}}^{\prime }$ is investigated using the data of the DIANA experiment. The distribution of the $p{K}^0$ effective mass shows a prominent enhancement near 1538 MeV formed by nearly 80 events above the background, whose width is consistent with being entirely due to the experimental resolution. Under the selections based on a simulation of $K^{+}$Xe collisions, the statistical significance of the signal reaches 5.5$\sigma$. We interpret this observation as strong evidence for formation of a pentaquark baryon with positive strangeness, ${\Theta }^{+}\left(uudd\overline{s}\right)$, in the charge-exchange reaction $K^{+}n\to K^{0}p$ on a bound neutron. The mass of the ${\Theta }^{+}$ baryon is measured as $m\left({\Theta }^{+}\right)=1538\pm 2$ MeV. Using the ratio between the numbers of resonant and nonresonant charge-exchange events in the peak region, the intrinsic width of this baryon resonance is determined as $\Gamma \left({\Theta }^{+}\right)=0.34\pm 0.10$ MeV.